<?php
abstract class  Circle
{
    private  $r;
    public function __construct($r)
    {
        $this->r=$r;
    }
    public function __clone()
    {
        $this->r=10;

    }
    public  function _toString()
    {
        return 'circle.r='.$this->r;
    }
    public function __call($methodname, $args)
    {
        die("你".$methodname."不存在");
    }


    public abstract function  getArea();

    public function __sleep()
    {
        return array("r");
    }


}


$c=new Circle(3);
$d=$c;
$cc=clone $c;
var_dump($c);
var_dump($d);
?>